It was the first time a monthly temperature anomaly had exceeded 1 degree, NOAA said.

Advertisement

The world's oceans are warming up along with the rest of the planet.

Photo: Leigh Henneingham

Land temperatures last month were 1.89 degrees above average, smashing the previous record departure from the norm, set in December 2006, by almost half a degree (0.48 degrees).

Sea temperatures were 0.83 degrees warmer than the 20th-century average, beating the previous record anomaly for December 2009 by 0.36 degrees.

The December surge came during a month when leaders from almost 200 nations gathered in Paris to set a new agreement to keep temperature increases to less than 2 degrees and reduce the risk of dangerous climate change.

Temperatures are rising about 0.17 degrees per decade since 1970, NOAA said.

During El Nino years, the Pacific Ocean's normally westward-blowing winds stall or reverse, leading to a warming of the central and eastern Pacific. Global temperatures get a kick of about 0.1-0.2 degree during such events.

The current El Nino - among the three strongest on record - probably peaked at the end of last year. The temperature impacts on the globe, though, typically lag about six months so it is likely that the start of 2016 will also be exceptionally warm, Dr Jones said.

The gap between last year and all previous record hot years was wide and widening by the end of 2015, as the following NOAA chart shows:

All of the 16 warmest years on record have happened since 1998, NOAA said.

Regional heat

The unusual warmth was widespread, with the Indian Ocean among those regions posting record heat.

Asia and South America had their hottest year on record, while Africa and Europe posted their second hottest years.

The US and Australia had their fifth hottest years on record, NOAA said.

Australia was about 0.8 degrees above average in 2015, or not far short of the global anomaly.

Land temperatures worldwide, though, were 1.33 degrees above average, beating the previous record departure from the norm by a quarter of a degree.

Australia's famously variable climate can cause annual temperatures to gyrate about 1 degree compared with the long-term average, while global shifts are in the order of 0.2-0.3 degrees, Dr Jones said.

While temperature changes were worth highlighting, people may also experience climate change through altered rainfall patterns and rising extremes, such as fire weather, he said.

Australia's fire season is already a particularly active one, with widespread fires in Victoria, South Australia, Western Australia and Tasmania - with at least another month of high fire risk to come.